General > General Technical Chat
The US electrical system
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themadhippy:

--- Quote ---If you want to see a sky extremely polluted with overhead wires, go to urban Japan.
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Their mere amateurs,try Thailand Cambodia or Vietnam to see how the professionals do it.
james_s:

--- Quote from: richard.cs on July 02, 2020, 04:25:27 pm ---
--- Quote from: IanB on July 02, 2020, 02:06:33 am ---Apparently it can happen that the 7200 V line can fall onto the telephone or CATV line strung lower down the pole, and cause problems (occasionally fatal) in connected homes.

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We don't share telephone etc. with HV poles here (UK), poles can have HV and LV or LV and signal stuff (but is possibly discouraged now?) but not HV and signals. Generally we have less overhead distribution in urban areas compared to what I have seen of the USA, and near-zero overhead HV in towns.

We have a lot of overhead LV and overhead telephone in older suburban areas, but all but the most rural newbuilds have all the cabling underground. Likely more to do with maintenance costs than safety, all the urban overhead LV was installed when labour was a lot cheaper.

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Underground wiring is far more expensive to install and maintain than overhead. While it's true that it isn't as prone to damage in wind storms that knock trees down it's not immune, a root ball from a fallen tree can really do a number on underground wires. It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry and have relatively few trees though.
TimFox:
A big advantage of underground wire in my part of the country is less problems with ice storms.
AlbertL:

--- Quote from: helius on July 01, 2020, 05:36:38 am ---
--- Quote from: AlbertL on June 30, 2020, 09:49:04 pm ---So, here's a question: what would be the resulting voltage at the customer's premises (bottom of the drawing) in the case of an accidental short between the ungrounded side of the distribution transformer primary (7200V) and one end of the 240V secondary?
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Which end, the side linked in-phase with the primary, or the other side?

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Good point - I hadn't considered the phasing aspect.   I think in the electrical power world they call that "polarity" even though it's referring to AC.
james_s:
Underground certainly has advantages, but it's not a panacea. Every time we have a big storm, especially the once in a decade kind a bunch of people start moaning that we should redo everything to underground. They have no clue how much it would cost and think it will solve all the problems, but it won't.
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